1. Field of the Disclosure
This disclosure relates generally to oilfield downhole tools and more particularly to drilling assemblies utilized for extended reach drilling operations.
2. Background of the Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to the bottom of a drilling assembly (also referred to herein as a “Bottom Hole Assembly” or (“BHA”). The drilling assembly is attached to the bottom of a tubing, which is usually either a jointed rigid pipe or a relatively flexible spoolable tubing commonly referred to in the art as “coiled tubing.” The string comprising the tubing and the drilling assembly is usually referred to as the “drill string.” When jointed pipe is utilized as the tubing, the drill bit is rotated by rotating the jointed pipe from the surface and/or by a mud motor contained in the drilling assembly. In the case of a coiled tubing, the drill bit is rotated by the mud motor. During drilling, a drilling fluid (also referred to as the “mud”) is supplied under pressure into the tubing. The drilling fluid passes through the drilling assembly and then discharges at the drill bit bottom. The drilling fluid provides lubrication to the drill bit and carries to the surface rock pieces disintegrated by the drill bit in drilling the wellbore. The mud motor is rotated by the drilling fluid passing through the drilling assembly. A drive shaft connected to the motor and the drill bit rotates the drill bit.
A substantial proportion of current drilling activity involves drilling deviated wellbores to more fully exploit hydrocarbon reservoirs. A deviated wellbore is a wellbore that is not vertical (e.g., a horizontal). The deviated section of such a borehole can extend thousands of feet from a vertical section of that wellbore. Conventionally, the weight of the drill string in the vertical section provides the weight on bit (WOB) needed to press the drill bit against the formation during drilling. As the length of the deviated sections increase, the available WOB diminishes due to drag forces and other environmental factors. The present disclosure addresses the need to provide WOB in instances where the weight of the drill string is insufficient to maintain the WOB needed for efficient cutting of the formation, as well as other needs of the prior art.